Ive just bought a Dec 2008 unaltered KLX 250S here in NZ with 5000 ks and it runs and handles really sweet. I have read they are too heavily restricted.. i am not sure but maybe it does seem a bit starved or something.....

I see it has a Canada sticker on the frame. My questions are:

-Are the Canada models less restricted to start with?

-Is there a couple of simple mods I can make that will help the bike 'breath' or run easier without costing me a lot of trial and error time and money, and without increasing the exaust noise or fuel consumption.

You see I am fairly happy with the bikes performance as it is - I just dont like the thought it has been set up too heavily restricted to meet some overly strict emission regulations - and that this actually puts a strain on the motor.

I have read many of the posts/threads on this subject and this question remains in my mind.
I cannot find a post that clarifies this point: Is there a tuning point that unrestricts the motor just enought to allow it to run at its best,(quite, relaxed, long life, potential, and is this as stock or not?

Thanks in advance!

 

ACOLE lives in UnZud. Wait until he chimes in with some info on your NZ spec bike. Not sure if the AUS bikes are the same 100% but pretty sure we get the real deal (USA spec bikes are corked more for sure bra. Beached as eh bra. LOL.)

 

One comment you made about "straining" the engine if it is too restrictive: you do not make the engine strain by restricting it.

An ICE is essentially an air pump, and it depends as much on intake of air as it does exhaust of hot air...but, if you restrict the exhaust, there is no strain....it simply has less call for intake air at that point. If you restrict the intake, there is no strain, it just has less need for a large exhaust at that point.

So, don't fret about straining it because of it's restrictive exhaust and/or intake. You make it "strain" when you turbocharge it. You make it strain when you are at Redline. You make it strain when you give it WOT at low rpms or when it "chugs" up a steep hill in too low of a gear.

Enjoy the bike, and find ways to increase it's ability to pull in, as well as exhaust air, and it will have more pep (which isn't the same as strain!).

 

"So, don't fret about straining it because of it's restrictive exhaust and/or intake."

Thanks Blackheart58 - you sound like you know your stuff. That helps, maybe I can just leave it the way it is...

But perhaps my use of the word 'straining' was not quite right. I mean can it be running so restricted that the mixture is too lean - or something else is set less than optimum in order to control the emissions? ....and the valves or something are stressed - I think you are saying that can't be so...?

 

[QUOTE=keeen;426862 But perhaps my use of the word 'straining' was not quite right. I mean can it be running so restricted that the mixture is too lean - or something else is set less than optimum in order to control the emissions? ....and the valves or something are stressed - I think you are saying that can't be so...?[/QUOTE]

The more restricted, the more RICH it runs.

Running it UNRESTRICTED can easily cause it to be running lean...which CAN burn things up, such as valves, piston tops, etc. That's why you have to put in larger fuel jets when you begin opening up the airbox and exhaust, to richen the fuel mixture as you unrestrict it.

You will NOT "stress" the engine by running it with stock carb setups with stock airbox and exhaust.

 

Keen I suspect your bike is jetted the way the AUS bikes are. They run sweet from the factory with #132 main jet and #35 pilot (USA bikes get chocked and leaned out from the factory with #118 main jet and #35 pilot jet. You only need to rejet if you add a full pipe or slip on pipe.

Change to a TwinAir or Uni air filter and it'll run a little sweeter. Remove the snorkel from the airbox lid at the same time but leave the lid in place with the stock pipe fitted.

 

Thanks guys - I am beginning to understand.

So the twinair or uni air filter less snorkel must let in slightly more air - but not enough for it to be too lean with the standard carb setup...?

My first tank got me 170 k from 7.1 litres = 24 k per litre - mostly short road trips - is that about right?

My last bike was a 650 Funduro and I am amazed how well this little 250 runs. Its very cold today so I just went for a short ride - pulled quite well up to 130 k ! - thats about the limit though - any faster depends on the wind direction!... Still its way better than the Funduro on the tight windies and gravel roads. Bundle of fun - roll on summer.

 

If you have the US model, I wouldn't change to a more free-flowing air filter or take off the snorkel, UNLESS I changed to a bigger jet. I don't know enough about other models, although I HEAR that they have bigger stock jets than the US model, so, they might be fine.

You are certainly correct to want to avoid overly lean.

Sorry, I can't comment on your fuel mileage, I'm too stupid to do the conversions to miles per gallon. Mine has gotten in the mid-60's the two tanks I've run through it. Mostly desert trails on those two tanks, fwiw.

 

Thanks - 60 MP USA G = 25 k per litre - so I got about 59 MPG on my first run. Humm..
maybe it is less restricted! Can the stock USA model pull up to about 130 k per hour ( thats 81 mile per hour)....

 

I'd think mine can do that Indicated Speed, as I've ridden it over 70 mph a few times, and it still has some throttle remaining. What the ACTUAL speed is, I don't know. I could get out a GPS to test it, but, it only has 300 something miles on it. Although I wring it out every once in a while, that's not as hard on it as running it WOT for over a minute to get it to top speed.